This section summarises:
- the technical framework underpinning licensing in the 2 GHz band;
- the operation of the section 145 Determination of Unacceptable Interference;
- the Advisory Guidelines that manage in-band and out-of band interference with other services; and
- other important information about the technical framework.
The technical framework for the 2 GHz band has been established by the ACMA to primarily support third generation mobile telecommunications services utilising any of the range of ITU designated IMT-2000 systems. It has evolved from the technical frameworks of previous spectrum licence allocations, in particular those for the 800 MHz and 1.8 GHz bands. The framework seeks to minimise negotiation necessary between adjacent licensees for the management of in-band and out-of-band interference in most circumstances. Nonetheless, spectrum licensees may negotiate among themselves and, where relevant, with apparatus licensees, for alternative management arrangements about emission levels. Spectrum licensees should note, however, that alternative arrangements are not possible unless all affected and potentially affected licensees agree.
Included in these flexibility provisions is a prescribed Form of Agreement (included in the Radiocommunications Spectrum Marketing Plan (2 GHz Band) 2000. The Form of Agreement provides a template for any agreements that relate to spectrum licensees agreeing to accept emissions that would, in the absence of those agreements, exceed the core conditions of their spectrum licence(s). For example, spectrum licensees might agree alternative arrangements with other licensees for higher levels of emission outside the frequency band of the spectrum licence, or for higher levels of radiated power across a geographic area boundary, than would have otherwise been allowed. Flexibility within the core conditions of licence gives effect to such arrangements between licensees. Applicants are advised to carefully review the arrangements set out for agreements between spectrum licensees, and between spectrum licensees and others, contained in the Radiocommunications Spectrum Marketing Plan (2 GHz Band) 2000.
The inherent flexibility of a spectrum licence acquired in this allocation is left for the licensee to determine. This should, however, be based on a careful technical and commercial assessment before the auction, in order to confirm that the desired spectrum space is sufficient to sustain the performance of the network and equipment the bidder desires to operate. The spectrum lots and subsequently issued licences are not predesigned to accommodate any particular network design. They may accommodate the operation of a particular technology, as well as non-standard equipment, at a particular location and frequency, depending on the size and shape of the licence that a bidder acquires.
The technical framework is crafted using three regulatory elements:
- licence core conditions, which are mandatory requirements made under the section 66 of the Act;
- a Determination of Unacceptable Interference for the purpose of device registration, made under section 145 of the Act; and
- Radiocommunications Advisory Guidelines made under section 262 of the Act.
The licence core conditions and the determination of unacceptable interference are used to keep significant levels of emission within the spectrum space of the licence. The advisory guidelines provide a framework for the management of interference with specific devices as required, usually associated with apparatus-licensed and class licensed services operating within the limits of the 2 GHz band and surrounding spectrum.
The technical framework is predicated on the assumption that:
- spectrum and apparatus licensees will employ good engineering practice in establishing and maintaining their services;
- receivers employed by spectrum licensees will, as a minimum, meet the minimum receiver performance levels set out in Schedule 1 of the Radiocommunications Advisory Guidelines (Managing Interference from Apparatus-licensed and Class-Licensed Transmitters — 2 GHz Band) 2000; and
- spectrum licensees will be responsible for managing interference that they, or authorised third parties, cause to their own services.
The following general principles are pertinent to this technical framework:
- the ACMA has attempted to provide maximum flexibility to spectrum licensees to establish services;
- Emission limits have been specified as absolute power levels (in EIRP) rather than power levels relative to transmitter power, allowing licensees to strike a balance between the maximum radiated power of a device and its out-of-band performance;
- The core conditions indirectly specify frequency stability by requiring the emission limits outside the band to be maintained under all conditions. A licensee is able to balance device emission bandwidth against frequency stability, by providing internal ‘guard bands’ as necessary;
Spectrum licensees have the responsibility to manage interference that arises within 200 metres of devices registered under their licences.
The interference mechanisms that the technical framework seeks to manage are those caused by:
- unwanted in-band emissions;
- emissions falling outside the frequency band of the licence; and
- intermodulation effects.
These mechanisms are dealt with by a combination of the core conditions relating to out-of-area and out-of-band emissions and those parts of the registration process which give effect to those conditions at the point of registration of devices prior to their operation.
It should be noted that agreements between licensees can only continue to apply while the size and the shape of the spectrum space owned by licensees remain unchanged. Where trading of licences takes place and new boundaries are formed, these agreements will need to be re-negotiated. This re-negotiation can occur at any time, that is, before or after the trade, so that there is no loss of flexibility to licensees.
When trading occurs by means of the division of spectrum space, and agreements are not in place, a check will be required to ensure that existing devices still meet the requirements of the licence within the changed spectrum space. The comments made within this section indicating how the interference management regime might affect proposed services and spectrum utility are not intended to be exhaustive. Potential spectrum licensees are reminded to take such expert technical and other advice necessary to inform themselves of possible effects on their proposed services.
Licence core conditions
This part of the section explains what the core conditions of the licence are intended to achieve (a sample licence can be found in Schedule 5 of the Radiocommunications Spectrum Marketing Plan (2 GHz Band) 2000), and how the emissions subject to those conditions are further managed under the technical framework.
For each licence, the core conditions set out:
- the geographic area;
- the frequency band;
- the out-of-area emission limits; and
- the out-of-band emission limits.
The geographic area or aggregate of areas within which the operation of radiocommunications devices is authorised by the licence is described in Part 3 of Licence Schedule 1.
The frequency band of the licence within which the operation of radiocommunications devices is authorised by the licence consists of the contiguous range of frequencies between the upper and lower frequency limit set out in Part 2 of Licence Schedule 1.
Out-of-area emission limits, through the Determination of Unacceptable Interference, protect geographically adjacent licensees. A fixed transmitter operated under a 2 GHz spectrum licence may be located anywhere in the geographic area of the licence. However, emissions from the transmitter must not cause the radiated powers outside the geographic bounds of the licence to exceed the limit imposed by core conditions 3 to 7 of the licence; as mentioned previously these limits can be extended by agreement with adjacent licensees.
The out-of-area power limit for a terrestrial transmitter in the 2 GHz Lower Band is a radiated power of 45 dBm/30 kHz. The out-of-area power limit for a terrestrial transmitter in the 2 GHz Upper Bands A and B is a radiated power of 55 dBm/30 kHz. In the case of a high altitude platform (HAPS)1 transmitter, the out-of-area limit is specified as a power flux density (pfd) limit of -136 dB(W /(m2⋅30 kHz)) at any point on the earth’s surface outside the licence area.
Note that the definition of the out-of-area limit for terrestrial transmitters effectively places a cap on the radiated power of transmitters anywhere in the area of the licence. An additional layer of out-of-area management is imposed at the point of registration of devices; this is discussed in detail in the later section “Determination of Unacceptable Interference”.
Out-of-band emission limits, through the Determination of Unacceptable Interference, protect licensees in adjacent spectrum. Out-of-band emission limits are imposed by core conditions 8 to 15 of the licence. A licensee or accredited person must work out the radiated power of the device within specified bandwidths outside the frequency band of the licence using good engineering practice to establish whether the operation of a device will breach these emission limits, causing ‘unacceptable interference’. Out-of-band emission limits have been expressed in the form of absolute levels, rather than levels relative to the transmitter output power, to allow licensees to operate transmitters with an optimised balance between transmit power and out-of-band emission suppression. These levels may be varied through negotiated agreement with affected adjacent licensees. If the power calculated is greater than a figure specified in the relevant licence condition, two things follow:
- if the device is not yet registered — the ACMA will generally refuse to register it,because the interference that it would cause will be ‘unacceptable interference’ within the meaning of section 145 of the Act, (unless, for example, all relevant licensees agree alternative arrangements);
- if the device is already registered — there will be a breach of the core licence condition, unless all relevant licensees have agreed to the alternative arrangements.
The limits for out-of-band emissions have been chosen to enable adjacent STU operation for systems located more than 200 metres apart (within this distance additional interference management measures may need to be taken by licensees — see next section).
Other licence conditions
Whilst core conditions go some way to limit interference to adjacent services their primary purpose is to define the spectrum space (geographic and frequency) of the spectrum licence. Some additional protection from interference may be required beyond that provided indirectly through the core conditions. One method of implementing this protection is by including other conditions in the licence.
Interference management at sites The licence includes a condition requiring the licensee to manage interference within 200 metres of a device operated under this licence. This condition has been included
due to the difficulty in specifying emission limits to prevent interference between a large range of services that may operate in close proximity at prime radiocommunications sites.
To manage out-of-band interference, spectrum licensees may for example have to utilize guard bands between licensees, install filters at the edges of their spectrum, and/or negotiate with adjacent licensees either to employ transmitter filtering or avoid placing transmitters near the frequency boundary at certain locations.
Determination of unacceptable interference
Before a transmitter can be operated under a spectrum licence its details must be recorded in the register. The ACMA may refuse to register a device if the licensee or accredited person cannot show that the requirements deemed to prevent unacceptable interference are met. These requirements are detailed in the relevant determination made by the ACMA under section 145 of the Act — the Radiocommunications (Unacceptable Levels of Interference – 2 GHz Band) Determination 2000.
The Determination sets out basic requirements to manage unacceptable levels of interference:
- that the core conditions of the licence are met;
- that specified device boundary criteria are met;
- that specified device deployment constraints are met; and
- that full details of the transmitter are provided for the register.
Device Boundary Criteria (DBC)
When issuing an interference impact certificate and registering a device in accordance with the Radiocommunications (Unacceptable Levels of Interference – 2 GHz Band) Determination 2000, a licensee or accredited person must, in addition to checking that the core conditions are maintained, calculate the device boundary of the transmitter as detailed in this determination. This involves establishing the distance, along radials from the transmitter, that is required for the emission level to drop below a level that is likely to cause interference to receivers in adjacent geographic areas. The distance along each radial is based on a mathematical propagation model. The device boundary method takes account of the terrain loss by adjusting the antenna height of a device according to its height above average terrain, called its effective antenna height. Effective antenna heights are calculated every 5 minutes in distance along each radial. The DBC for the 2 GHz band makes use of the ACMAs digital elevation model, RadDEM, for height calculations. RadDEM is referenced to the Australian Geodetic Datum 1966. The ACMA publishes software tools on the RadDEM CD for calculating tables of effective antenna heights for any location in Australia using the DBC methodology relevant to the 2 GHz band.
The effect of the device boundary procedure is to create ‘buffer zones’ of reduced emissions along the geographic boundaries of a licence. It is an important element of the framework because it specifies an exact and direct procedure to determine the allowed maximum radiated power of a transmitter (based on the effective antenna height and distance from the boundary) that cannot be challenged by an adjacent licensee. The direct nature of the limit means that licensees can work closer to the geographic boundary of the licence than otherwise because no reliability margins are required to ensure specified field strengths occurs at a boundary. In addition, licensees can accurately plan for transmitters operated by adjacent spectrum licensees across the area boundary at any time in the future. Also, the device boundary may or may not be based on actual propagation models depending on the outcome required. Additionally, it provides a simple facility for establishing agreements between licensees for sharing spectrum space across area boundaries by employing a single parameter (‘S’, the ‘device boundary scaling parameter’, mentioned in the Device Boundary Criteria) which may be varied to expand or contract the device boundary to provide more or less in-band protection respectively.
If the device boundary falls outside the geographic area of the relevant spectrum licence the ACMA will, generally speaking, refuse to register the device because the levels of emission outside the licence that it would cause will be ‘unacceptable interference’ within the meaning of section 145 of the Act. An exception to this general rule can be made where there is an agreement in the form prescribed in the Radiocommunications Spectrum Marketing Plan (2 GHz Band) 2000. In these circumstances, the agreement provides that a device boundary may exceed the licence boundary of a licensee because the adjacent licensee has specifically agreed to that and accepts any interference caused to its use of the spectrum.
Under the determination, a device boundary does not need to be established for:
- mobile or indoor fixed transmitters where the radiated power is less than 25 dBm per 30 kHz;
- any fixed transmitter located more than 70 km from any spectrum licence boundary; or
- a HAPS transmitter.
Whilst the two core conditions aimed at emission levels provide some measure of protection from intermodulation effects and other out-of-band interference, the ACMA considers it necessary to provide further means of protection to avoid close-range high site-to-high site (base station) interference paths. To this end the licensing framework imposes some constraints on the deployment of transmitters. It is, however, important to note that the technical framework does not provide any protection from these effects where transmitters are sited within 200 metres of each other. Consequently spectrum licences include a special condition requiring spectrum licensees to come to an arrangement with neighbours in relation to interference in such cases.
The deployment constraints vary from band to band. The constraints are generally expressed in terms of effective antenna height (calculated using the average ground height within approximately 10 kilometres of each device) or through limits on power levels. For a more detailed explanation of effective antenna height, please see the relevant section 145 determination.
For the 2 GHz band, deployment constraints are imposed in the Upper Band A to optimise the deployment opportunities for base receiver stations in this band, and also in the 2 GHz Lower Band to manage potential interference with class-licensed services in the spectrum below 1900 MHz.
Registration of devices
The ACMA will, generally speaking, refuse to register a device whenever it would give rise to levels of emission outside the licence that would be ‘unacceptable interference’ within the meaning of section 145 of the Act. Consequently, accredited persons are required to issue an Interference Impact Certificate (IIC) before a device will be registered.
The Radiocommunications (section 145(3) Certificates) Determination 2000 specifies three options for the issue of IICs in a spectrum licence. The general method for certification is through adherence to the requirements detailed in the relevant s.145 Determination for a band – see Radiocommunications (Unacceptable Levels of Interference – 2 GHz Band) Determination 2000.
The ACMA has also provided two alternative methods to issue an IIC, these are:
- where it is shown that there is sufficient internal guard space to manage potential interference within the spectrum space of the licensee; or
- where there is a written agreement in place with all affected licensees to accept higher levels of interference.
Guidance on the registrations of radiocommunications devices via guard space and agreements is provided in the information paper Registration of radiocommunications devices under spectrum licences.
The corollary of this aspect of interference management is that spectrum licensees must expect that certain levels of emission will legitimately cross their geographic (and spectrum) boundaries from points within other spectrum licensed areas. Accordingly, when considering what services they might establish within their own geographic areas, spectrum licensees should take into account the fact that transmitters may be located at certain points within other spectrum licensed areas. Furthermore, those transmitters may radiate power into the spectrum licensee’s area at any level up to that allowed under the relevant section 145 determination of unacceptable interference, or levels otherwise negotiated with the relevant spectrum licensees. The ACMA recommends that radio-communications devices are registered at the system design stage. This will enable other licensees, if they wish, to re-check the coordination and if an obvious error is detected, negotiate directly with the spectrum licensee before further costs are incurred when transmitters cannot be operated due to interference. The registration of devices never intended for operation is not recommended because this has the potential to inhibit unnecessarily the operation of adjacent licensees’ devices.
Registering groups of transmitters and receivers
The Determination also sets out the definition of a group of transmitters and a group of receivers for the purpose of simplifying registration of those devices. The Determination specifies how the registration details for a group of transmitters and receivers must be calculated. Unless exempted, transmitters must always be registered as either an individual transmitter or as part of a group of transmitters. If two or more transmitters are operated for the purpose of communicating with the same receiver or same group of receivers and they have identical emission characteristics, then those transmitters may be treated as a group in order to simplify the registration process. A transmitter may belong to more than one group.
Groups are defined to help minimise the work associated with the registration process of similar transmitters. A group of devices may have location details consisting of a centre and an associated effective radius that can take into account the distribution of subscriber transmitters. Mobile and indoor transmitters are exempted from device registration requirements. Licensees may decide whether to register receivers based on a risk assessment of the benefits achieved through coordination to manage out-of-band interference.
Radiocommunications advisory guidelines
There are two Radiocommunications Advisory Guidelines made under section 262 of the Act issued by the ACMA associated with spectrum licensing of the 2 GHz band. They are:
- Radiocommunications Advisory Guidelines (Managing Interference from Apparatus and Class-licensed Transmitters—2 GHz band) 2000; and
- Radiocommunications Advisory Guidelines (Protection of Apparatus-licensed and Class-licensed Receivers—2 GHz band) 2000.
These guidelines do not bind licensees or the ACMA. This approach has been adopted in order to provide the maximum flexibility for both spectrum and apparatus licensees in how they arrange their affairs so as to avoid interference between services. The ACMA is prepared to consider alternative interference management arrangements agreed between spectrum licensees and, where relevant, apparatus licensees. Spectrum licensees should note, however, that the ACMA would not give effect to alternative arrangements unless all affected and potentially affected licensees have agreed (subsequent trading of spectrum will affect any agreements made previously). Licensees who are unable to resolve interference issues between themselves may expect the ACMA to have regard to the guidelines in dealing with such disputes.
Managing interference from apparatus-licensed and class-licensed transmitters
The Radiocommunications Advisory Guidelines (Managing Interference from Apparatus and Class-licensed Transmitters—2 GHz band) 2000 contains information for spectrum licensees on managing interference from non-spectrum-licensed services.
Only registered receivers will receive protection in the planning of services by the ACMA. For the management of interference from out-of-band services, the ACMA in this guideline has set out a minimum performance level for receivers in the 2 GHz band and a compatibility requirement for transmitters of apparatus-licensed services. These criteria provide a basis upon which spectrum and apparatus licensees are able to develop procedures for the management of interference between services, using good engineering practice.
As mentioned previously, licensees will need to take account of the emission limits permitted under the technical framework when deciding the level of performance they require for their receivers. Receivers will cope with emission levels with differing degrees of success, depending on their interference susceptibility. A receiver with poor performance would normally deny large amounts of spectrum space for transmitters in order to protect it from interference. The ACMA does not intend to enforce receiver standards. It is for licensees to balance the cost of receiver performance against the cost of spectrum space denied to their transmitters. Poor receiver performance is only an issue when a licensee attempts to use spectrum space belonging to an adjacent licensee as part of the receiver protection requirement.
The framework provides for the operation of receivers that have interference susceptibility commensurate with that achieved by current technology and intends for this level of performance to guide the interference settlement process. Receivers with poor interference susceptibility performance can be used, but in those cases licensees may have to use more of their own spectrum space as guard space. For example, interference that results from a receiver having a RF or IF bandwidth that is larger than the frequency band of the licence will be the licensee’s responsibility. It is the licensee’s responsibility to use receivers in a manner that is both consistent with good engineering practice and effectively copes with the levels of emissions permitted under the technical framework.
Protecting apparatus-licensed and class-licensed receivers
The Radiocommunications Advisory Guidelines (Protection of Apparatus-licensed and Class-licensed Receivers—2 GHz band) 2000 contains information for spectrum licensees regarding protection they should provide to non-spectrum-licensed receivers. These guidelines relate to the protection of receivers of a number of services operating in or near the 2 GHz band, including:
- microwave fixed point-to-point services;
- the mobile satellite service;
- cordless telecommunications services;
- multipoint distribution services; and
- space services.
Interference that the technical framework does not prevent
No matter how rigorous the engineering analysis of a device, there is always a possibility of actual interference when devices are deployed in the field. This is because the technical framework is designed according to certain levels of acceptable interference probability. Under the framework described here, it is anticipated that interference between spectrum licensed devices will occur at about the same rate as between apparatus licensed devices, that is, interference will arise in fewer than one percent of cases. Such interference may be caused by emissions at frequencies either inside or outside licensees’ spectrum space.
Licensees are strongly advised before making an interference complaint to attempt to locate the source of any interference by checking the Register of Radiocommunications Licences. This investigation may indicate the likely cause of the interference and it may be possible to settle the problem without the ACMA’s intervention. If the ACMA becomes involved, licensees may be charged for any work undertaken.
The ITU Radio Regulations have international treaty status and are binding on Australia. Transmitters operated under a spectrum licence, other than in accordance with ITU Radio Regulations, must not cause interference to any services of any other country (for example, Papua New Guinea or Indonesia) which are operating in accordance with ITU Radio Regulations. If operation of a transmitter does cause harmful interference to overseas services operating in accordance with ITU Radio Regulations, the transmission must cease. Spectrum licensees must also accept interference from any overseas service operating in accordance with ITU regulations. Spectrum licensees should note that the ACMA will impose such additional licence conditions on spectrum licences as may be necessary from time to time to meet Australia’s international obligations.
Health and safety
Every spectrum licensee will need to take into account occupational health and safety requirements for radiofrequency devices. Occupational health and safety requirements that concern use of radiofrequency devices are currently the responsibility of State and Territory Governments. In addition, licensees will be required to comply with any health exposure standards that may be made by the ACMA for the health and safety of persons who operate, work on or use radiocommunications transmitters and receivers.
Environmental and other considerations
A spectrum licence only authorises the operation of devices, and does not confer any rights on the licensee to erect infrastructure. Antenna siting, height and construction may be regulated by State, Territory or local government legislation. Licensees should investigate the local rules pertaining to the erection of towers and antennas before planning for a device to operate in a certain location. However, the holders of carrier licences under the Telecommunications Act 1997 may, in some circumstances, obtain limited immunity from such legislation for the erection of certain infrastructure. The ACMA recommends that applicants seek legal and other specialist advice on this issue.
Obtaining a permit to operate non-standard devices
A licensee who wishes to operate standard devices under a spectrum licence (that is, equipment that conforms to mandatory ACMA standards) does not need to apply to the ACMA for permission to do so. However, a permit will be required to supply or operate any non-standard devices. These permits may be issued by the ACMA under section 167 of the Radiocommunications Act 1992, and will only be issued during the term of the licence. Permits to supply non-standard devices for operation under a spectrum licence may also be issued by the ACMA under section 174 of the Act.